In an LTE system, control data used to assist service data demodulation is transmitted on a physical downlink control channel (Physical Downlink Control Channel, PDCCH for short) and generally in an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short) manner. The PDCCH includes resources distributed in a time domain and a frequency domain, and may be referred to as a downlink control channel resource (briefly referred to as a downlink resource). The downlink resource is divided into multiple OFDM symbols in the time domain, and is divided into multiple subcarriers in the frequency domain. A subcarrier in an OFDM symbol is referred to as a resource element (Resource Element, RE for short). When transmitting control data to a terminal in the downlink, a base station needs to establish a mapping relationship between an RE that carries the control data and an antenna port, so that the base station can match the control data carried by the RE with the antenna port according to the mapping relationship, and modulate and send the control data by using a reference signal of the antenna port. On a terminal side, the control data carried by the RE also needs to be demodulated according to the mapping relationship by using the reference signal corresponding to the antenna port corresponding to the RE.
In the prior art, for example, in the LTE Release 8/9/10, control data in each subframe is carried by REs in the first several OFDM symbols in the subframe, and REs in remaining OFDM symbols are used to carry service data. As LTE technologies are evolving to the LTE Release 11/12, the capacity of a downlink control channel needs to increase, so does the need to use an entire subframe, instead of several OFDM symbols, to transmit control data. Such a control channel may be referred to as an enhanced physical downlink control channel (Enhanced PDCCH, ePDCCH for short). However, it is not yet explicitly defined in which manner a mapping is established between a resource on the ePDCCH (which may be referred to as an enhanced downlink control channel resource) and an antenna port, which hinders LTE development.